docs: def get_hcurves(self, imtls=None):
          """
          :param imtls: intensity measure types and levels
          :returns: an array of (R, N) hazard curves
          """
          self.init()
          if imtls is None:
              imtls = self.imtls
          pmaps = [pmap.convert2(imtls, self.sids)
                   for pmap in self.get_pmaps()]
          return numpy.array(pmaps)